1. Field of the Invention
The present invention relates to a power supply system for a boat.
2. Description of the Related Art
Some boats are provided with a power supply system in which a three phase alternating-current generator provided for a boat propulsion system generates a current, and the generated current is supplied to a main electric system which includes a main battery for supplying electric power to a control system of the boat propulsion system and to an auxiliary electric system which includes an auxiliary battery for supplying electric power to boat equipment or the like. In recent years, it has become common for the boat equipment to include auxiliary devices such as a bow thruster or an air conditioner, which consume a large amount of electric power. When a load is increased due to the boat equipment as described above, the generated current flows for the most part into the auxiliary electric system side, with the result that the main battery side suffers a voltage drop.
In view of the above-mentioned problem, there has been conventionally proposed a technology in which when a voltage drop in the main battery is detected, current supply to the auxiliary electric system is stopped, to thereby prevent the voltage drop in the main battery (see JP 2007-110855 A).
Meanwhile, in a case where the boat is equipped with an actuating device, such as a power steering device, which momentarily requires a high current while being required to have high system performance (hereinafter, a description is given by taking power steering as an example), it is necessary to cause the steering motor to instantaneously operate in response to the operation of the steering unit. However, as in the case of the conventional technology described above, when the auxiliary electric system is isolated after a voltage drop in the main battery is detected, the voltage of the main electric system has already dropped when driving the steering motor, which could affect the optimal drive performance of the steering motor.